KVC自定义实现
清楚了KVC的设值和取值流程，我们就可以自定义一下它的实现过程，代码如下：
- (void)lg_setValue:(nullable id)value forKey:(NSString *)key{ // KVC 自定义 // 1: 判断什么 key if (key == nil || key.length == 0) { return; } // 2: setter set<Key>: or _set<Key>, // key 要大写 NSString *Key = key.capitalizedString; // 拼接方法 NSString *setKey = [NSString stringWithFormat:@"set%@:",Key]; NSString *_setKey = [NSString stringWithFormat:@"_set%@:",Key]; NSString *setIsKey = [NSString stringWithFormat:@"setIs%@:",Key]; if ([self lg_performSelectorWithMethodName:setKey value:value]) { NSLog(@"*********%@**********",setKey); return; }else if ([self lg_performSelectorWithMethodName:_setKey value:value]) { NSLog(@"*********%@**********",_setKey); return; }else if ([self lg_performSelectorWithMethodName:setIsKey value:value]) { NSLog(@"*********%@**********",setIsKey); return; } // 3: 判断是否响应 accessInstanceVariablesDirectly 返回YES NO 奔溃 // 3:判断是否能够直接赋值实例变量 if (![self.class accessInstanceVariablesDirectly] ) { @throw [NSException exceptionWithName:@"LGUnknownKeyException" reason:[NSString stringWithFormat:@"****[%@ valueForUndefinedKey:]: this class is not key value coding-compliant for the key name.****",self] userInfo:nil]; } // 4: 间接变量 // 获取 ivar -> 遍历 containsObjct - // 4.1 定义一个收集实例变量的可变数组 NSMutableArray *mArray = [self getIvarListName]; // _<key> _is<Key> <key> is<Key> NSString *_key = [NSString stringWithFormat:@"_%@",key]; NSString *_isKey = [NSString stringWithFormat:@"_is%@",Key]; NSString *isKey = [NSString stringWithFormat:@"is%@",Key]; if ([mArray containsObject:_key]) { // 4.2 获取相应的 ivar Ivar ivar = class_getInstanceVariable([self class], _key.UTF8String); // 4.3 对相应的 ivar 设置值 object_setIvar(self , ivar, value); return; }else if ([mArray containsObject:_isKey]) { Ivar ivar = class_getInstanceVariable([self class], _isKey.UTF8String); object_setIvar(self , ivar, value); return; }else if ([mArray containsObject:key]) { Ivar ivar = class_getInstanceVariable([self class], key.UTF8String); object_setIvar(self , ivar, value); return; }else if ([mArray containsObject:isKey]) { Ivar ivar = class_getInstanceVariable([self class], isKey.UTF8String); object_setIvar(self , ivar, value); return; } // 5:如果找不到相关实例 @throw [NSException exceptionWithName:@"LGUnknownKeyException" reason:[NSString stringWithFormat:@"****[%@ %@]: this class is not key value coding-compliant for the key name.****",self,NSStringFromSelector(_cmd)] userInfo:nil]; } - (nullable id)lg_valueForKey:(NSString *)key{ // 1:刷选key 判断非空 if (key == nil || key.length == 0) { return nil; } // 2:找到相关方法 get<Key> <key> countOf<Key> objectIn<Key>AtIndex // key 要大写 NSString *Key = key.capitalizedString; // 拼接方法 NSString *getKey = [NSString stringWithFormat:@"get%@",Key]; NSString *countOfKey = [NSString stringWithFormat:@"countOf%@",Key]; NSString *objectInKeyAtIndex = [NSString stringWithFormat:@"objectIn%@AtIndex:",Key]; #pragma clang diagnostic push #pragma clang diagnostic ignored "-Warc-performSelector-leaks" if ([self respondsToSelector:NSSelectorFromString(getKey)]) { return [self performSelector:NSSelectorFromString(getKey)]; }else if ([self respondsToSelector:NSSelectorFromString(key)]){ return [self performSelector:NSSelectorFromString(key)]; }else if ([self respondsToSelector:NSSelectorFromString(countOfKey)]){ if ([self respondsToSelector:NSSelectorFromString(objectInKeyAtIndex)]) { int num = (int)[self performSelector:NSSelectorFromString(countOfKey)]; NSMutableArray *mArray = [NSMutableArray arrayWithCapacity:1]; for (int i = 0; i<num-1; i++) { num = (int)[self performSelector:NSSelectorFromString(countOfKey)]; } for (int j = 0; j<num; j++) { id objc = [self performSelector:NSSelectorFromString(objectInKeyAtIndex) withObject:@(num)]; [mArray addObject:objc]; } return mArray; } } #pragma clang diagnostic pop // 3:判断是否能够直接赋值实例变量 if (![self.class accessInstanceVariablesDirectly] ) { @throw [NSException exceptionWithName:@"LGUnknownKeyException" reason:[NSString stringWithFormat:@"****[%@ valueForUndefinedKey:]: this class is not key value coding-compliant for the key name.****",self] userInfo:nil]; } // 4.找相关实例变量进行赋值 // 4.1 定义一个收集实例变量的可变数组 NSMutableArray *mArray = [self getIvarListName]; // _<key> _is<Key> <key> is<Key> // _name -> _isName -> name -> isName NSString *_key = [NSString stringWithFormat:@"_%@",key]; NSString *_isKey = [NSString stringWithFormat:@"_is%@",Key]; NSString *isKey = [NSString stringWithFormat:@"is%@",Key]; if ([mArray containsObject:_key]) { Ivar ivar = class_getInstanceVariable([self class], _key.UTF8String); return object_getIvar(self, ivar);; }else if ([mArray containsObject:_isKey]) { Ivar ivar = class_getInstanceVariable([self class], _isKey.UTF8String); return object_getIvar(self, ivar);; }else if ([mArray containsObject:key]) { Ivar ivar = class_getInstanceVariable([self class], key.UTF8String); return object_getIvar(self, ivar);; }else if ([mArray containsObject:isKey]) { Ivar ivar = class_getInstanceVariable([self class], isKey.UTF8String); return object_getIvar(self, ivar);; } return @""; } #pragma mark - 相关方法 - (BOOL)lg_performSelectorWithMethodName:(NSString *)methodName value:(id)value{ if ([self respondsToSelector:NSSelectorFromString(methodName)]) { #pragma clang diagnostic push #pragma clang diagnostic ignored "-Warc-performSelector-leaks" [self performSelector:NSSelectorFromString(methodName) withObject:value]; #pragma clang diagnostic pop return YES; } return NO; } - (id)performSelectorWithMethodName:(NSString *)methodName{ if ([self respondsToSelector:NSSelectorFromString(methodName)]) { #pragma clang diagnostic push #pragma clang diagnostic ignored "-Warc-performSelector-leaks" return [self performSelector:NSSelectorFromString(methodName) ]; #pragma clang diagnostic pop } return nil; } - (NSMutableArray *)getIvarListName{ NSMutableArray *mArray = [NSMutableArray arrayWithCapacity:1]; unsigned int count = 0; Ivar *ivars = class_copyIvarList([self class], &count); for (int i = 0; i<count; i++) { Ivar ivar = ivars[i]; const char *ivarNameChar = ivar_getName(ivar); NSString *ivarName = [NSString stringWithUTF8String:ivarNameChar]; NSLog(@"ivarName == %@",ivarName); [mArray addObject:ivarName]; } free(ivars); return mArray; }
